1. Field of the Invention:
This invention relates to a device for locking a turbine rotor blade, wherein the rim of the rotor disk is provided with teeth formed by essentially axial grooves. The grooves are designed to accept the roof of the blades which are radially locked by wedges positioned between the blade roof and the bottom of the groove. Each blade roof is extended by a shank having a platform and a blade wherein the device of the invention comprises a locking piece which interacts with corresponding housings in the axial groove.
2. Description of the Prior Art:
Axial blade locking devices are known. The known devices include a lock which interacts with housings provided in the blade roof and in the axial groove into which the blade is inserted and radially maintained. This lock is kept in place by a wedge inserted between the bottom of the groove and the underside of the blade roof.
French Pat. No. 2,345,605 discloses a device of this type. The rim of the rotor disk comprises axial, dovetailed grooves which partially extend into a peripheral portion of the rim which protrudes relative to the surface of the disk. The blade roof include a tooth which corresponds to the protruding portion of the rim and which is provided with a transverse slot across its underside. Opposed radial slots are provided in the edges of the axial grooves. The lock is in the form of a U-shaped part, the outside surfaces of the lateral arms of which interact with the radial slots in the groove, and the transverse arm of which interacts with the transverse slot in the blade roof. The U-shaped part is inserted radially from the inside toward the outside into each slot and is kept in place by the end of the wedge inserted between the blade roof and the bottom of the groove. The wedge is axially maintained in a conventional manner by flanges on the nose cone and/or on the drum of the preceding or following rotor.
This device is reliable and easily assembled and disassembled. However, its disadvantage is that it requires a blade having a tooth and a protruding rim, the consequence of which is to increase the total mass of the rotor.
French Patent No. 2,273,155 describes a device which requires neither a blade tooth nor a protruding rim. The blade roof extremities are parallel; the blade does not include a tooth and the rim which bears the axial grooves does not have a protruding peripheral part. The axial grooves are dovetailed and are transversally separated by a peripheral groove parallel to the disk surfaces. The underside of the blade base is provided with two notches, an axial notch and a transverse notch, wherein the axial notch corresponds to a similar notch provided in the bottom of the axial groove, and the transverse notch corresponds to the peripheral groove.
The lock is formed of an elastic, elongated part with the same width as that of the groove, and displays in its center a transverse part forming a cross. The lock is placed in the groove in such a way that the transverse part is aligned with the notch at the bottom of the groove. When the blade is slipped into place in the groove, the lock is partially lodged in the axial and transverse notches of the blade base, and maintains the blade in the axial direction.
This device provides for a lower total rotor mass. However, its disadvantage is that it requires special tooling for installing or removing the blades.